Recently I needed to watch the size of a file I was downloading and see how the size was increasing. I came across the command watch on unix. According to manpage of watch:
watch - execute a program periodically, showing output fullscreen
watch -n 5 "du -h <file name>"
Sample Output: (fullscreen)
Every 5.0s: du -h ./<file name> Wed Feb 15 20:36:48 2017 2.5G ./<file name>